Light receiving element, distance measurement module, and electronic equipment

ABSTRACT

The present technology relates to a light receiving element, a distance measurement module, and electronic equipment which are capable of reducing leakage of incident light to adjacent pixels. A light receiving element includes a semiconductor layer in which photodiodes performing photoelectric conversion of infrared rays are formed in units of pixels, and a wiring layer in which a transfer transistor reading charge generated by the photodiodes is formed, and an inter-pixel light shielding unit that shields the infrared rays is formed at a pixel boundary portion of the wiring layer. The present technology can be applied to, for example, a distance measurement module that measures a distance to a subject, and the like.

TECHNICAL FIELD

The present technology relates to a light receiving element, a distancemeasurement module, and electronic equipment, and more particularly, toa light receiving element, a distance measurement module, and electronicequipment which are capable of reducing leakage of incident light toadjacent pixels.

BACKGROUND ART

In the related art, distance measurement systems using an indirect timeof flight (ToF) scheme are known. In such a distance measurement system,it is indispensable to include a sensor that can rapidly distributesignal charge, which is obtained by receiving reflected light of activelight reflected by an object, to different regions, the active lightbeing emitted using a light emitting diode (LED) or a laser at a certainphase.

Consequently, for example, a technique capable of rapidly modulating aregion in a wide range in a substrate of a sensor by directly applying avoltage to the substrate to generate current in the substrate has beenproposed (see, for example, PTL 1).

CITATION LIST

[PTL 1]

JP 2011-86904A

SUMMARY Technical Problem

In many cases, near infrared rays with a wavelength of approximately 940nm are used as a light source of a light receiving element used in anindirect ToF scheme. Since near infrared rays have a low absorptioncoefficient of silicon which is a semiconductor layer, and have lowquantum efficiency, a structure that increases quantum efficiency byextending an optical path length is conceivable, but there is concernabout leakage of incident light to adjacent pixels.

The present technology is contrived in view of such circumstances andcan make it possible to reduce leakage of incident light to adjacentpixels.

Solution to Problem

A light receiving element according to a first aspect of the presenttechnology includes a semiconductor layer in which photodiodesperforming photoelectric conversion of infrared rays are formed in unitsof pixels, and a wiring layer in which a transfer transistor readingcharge generated by the photodiodes is formed, in which an inter-pixellight shielding unit that shields the infrared rays is formed at a pixelboundary portion of the wiring layer.

A distance measurement module according to a second aspect of thepresent technology includes a predetermined light generation source anda light receiving element, in which the light receiving element includesa semiconductor layer in which photodiodes performing photoelectricconversion of infrared rays are formed in units of pixels, and a wiringlayer in which a transfer transistor reading charge generated by thephotodiodes is formed, and an inter-pixel light shielding unit thatshields the infrared rays is formed at a pixel boundary portion of thewiring layer.

Electronic equipment according to a third aspect of the presenttechnology includes a distance measurement module including apredetermined light generation source and a light receiving element, inwhich the light receiving element includes a semiconductor layer inwhich photodiodes performing photoelectric conversion of infrared raysare formed in units of pixels, and a wiring layer in which a transfertransistor reading charge generated by the photodiodes is formed, and aninter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.

In the first to third aspects of the present technology, a lightreceiving element is provided with a semiconductor layer in whichphotodiodes performing photoelectric conversion of infrared rays areformed in units of pixels, and a wiring layer in which a transfertransistor reading charge generated by the photodiodes is formed, and aninter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.

The light receiving element, the distance measurement module, and theelectronic equipment may be independent devices, or may be modulesincorporated into other devices.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a schematic configuration exampleof a light receiving element to which the present technology is applied.

FIG. 2 is a cross-sectional view illustrating a first configurationexample of pixels.

FIG. 3 is a diagram illustrating effects of an inter-pixel lightshielding unit.

FIG. 4 is a cross-sectional view illustrating a modification example ofthe first configuration example of pixels.

FIG. 5 is a diagram illustrating a circuit configuration example of thepixels in FIG. 2 .

FIG. 6 is a plan view illustrating an example of arrangement of a pixelcircuit in FIG. 4 .

FIG. 7 is a plan view illustrating other examples of formation of theinter-pixel light shielding unit.

FIG. 8 is a plan view illustrating other examples of formation of theinter-pixel light shielding unit.

FIG. 9 is a diagram illustrating other circuit configuration examples ofthe pixels in FIG. 2 .

FIG. 10 is a plan view illustrating an example of arrangement of a pixelcircuit in FIG. 9 .

FIG. 11 is a cross-sectional view illustrating a second configurationexample of pixels.

FIG. 12 is a cross-sectional view illustrating another example offormation of a moth eye structure portion.

FIG. 13 is a cross-sectional view illustrating a third configurationexample of pixels.

FIG. 14 is a diagram illustrating effects of a reflection film in FIG.13 .

FIG. 15 is a cross-sectional view illustrating a first modificationexample of the third configuration example of pixels.

FIG. 16 is a diagram illustrating effects of a reflection film in FIG.15 .

FIG. 17 is a cross-sectional view illustrating a second modificationexample of the third configuration example of pixels.

FIG. 18 is a cross-sectional view illustrating a fourth configurationexample of pixels.

FIG. 19 is a cross-sectional view illustrating a fifth configurationexample of pixels.

FIG. 20 is a cross-sectional view illustrating a sixth configurationexample of pixels.

FIG. 21 is a cross-sectional view illustrating a seventh configurationexample of pixels.

FIG. 22 is a cross-sectional view illustrating a modification example ofthe seventh configuration example of pixels.

FIG. 23 is a cross-sectional view illustrating an eighth configurationexample of pixels.

FIG. 24 is a cross-sectional view illustrating a modification example ofthe eighth configuration example of pixels.

FIG. 25 is a cross-sectional view illustrating a ninth configurationexample of pixels.

FIG. 26 is a diagram illustrating a circuit configuration example ofpixels in a case where the light receiving element is configured as anIR imaging sensor.

FIG. 27 is a cross-sectional view of pixels in a case where the lightreceiving element is configured as an IR imaging sensor.

FIG. 28 is a diagram illustrating an example of arrangement of pixels ina case where the light receiving element is configured as an RGBIRimaging sensor.

FIG. 29 is a block diagram illustrating a configuration example of adistance measurement module to which the present technology is applied.

FIG. 30 is a block diagram illustrating a configuration example of asmartphone as electronic equipment to which the present technology isapplied.

FIG. 31 is a block diagram illustrating an example of a schematicconfiguration of a vehicle control system.

FIG. 32 is diagram illustrating an example of installation positions ofa vehicle exterior information detection unit and an imaging unit.

DESCRIPTION OF EMBODIMENTS

Modes for embodying the present technology (hereinafter referred to asembodiments) will be described below. Note that the description will bemade in the following order.

1. Configuration example of light receiving element

2. Cross-sectional view according to first configuration example ofpixel

3. Modification example of first configuration example

4. Circuit configuration example of pixel

5. Plan view of pixel

6. Other circuit configuration example of pixel

7. Plan view of pixel

8. Cross-sectional view according to second configuration example ofpixel

9. Cross-sectional view according to third configuration example ofpixel

10. Modification example of third configuration example

11. Cross-sectional view according to fourth configuration example ofpixel

12. Cross-sectional view according to fifth configuration example ofpixel

13. Cross-sectional view according to sixth configuration example ofpixel

14. Cross-sectional view according to seventh configuration example ofpixel

15. Cross-sectional view according to eighth configuration example ofpixel

16. Cross-sectional view according to ninth configuration example ofpixel

17. Configuration example of IR imaging sensor

18. Configuration example of RGBIR imaging sensor

19. Configuration example of distance measurement module

20. Configuration example of electronic equipment

21. Example of application to moving body

Note that, in drawings to be referred to hereinafter, same or similarportions are denoted by same or similar reference signs. However, thedrawings are schematic and relationships between thicknesses and planview dimensions, ratios of thicknesses of respective layers, and thelike differ from those in reality. In addition, drawings includeportions where dimensional relationships and ratios differ between thedrawings.

In addition, definitions of directions such as up-down in the followingdescriptions are merely definitions provided for the sake of brevity andare not intended to limit the technical ideas of the present disclosure.For example, when an object is observed after being rotated by 90degrees, up-down is converted into and interpreted as left-right, andwhen an object is observed after being rotated by 180 degrees, up-downis interpreted as being inverted.

<1. Configuration Example of Light Receiving Element>

FIG. 1 is a block diagram illustrating a schematic configuration exampleof a light receiving element to which the present technology is applied.

A light receiving element 1 illustrated in FIG. 1 is a ToF sensor thatoutputs distance measurement information by an indirect ToF scheme.

The light receiving element 1 receives light (reflected light) obtainedby reflection of light emitted from a predetermined light source(irradiation light) and hitting against an object, and outputs a depthimage in which information on a distance to the object is stored asdepth values. Note that irradiation light emitted from a light sourceis, for example, infrared rays with a wavelength in a range from 780 nmto 1000 nm, and is pulse light of which turn-on and turn-off arerepeated in a predetermined cycle.

The light receiving element 1 includes a pixel array portion 21 formedon a semiconductor substrate not illustrated in the drawing, and aperipheral circuit portion integrated on the same semiconductorsubstrate as that of the pixel array portion 21. The peripheral circuitportion includes, for example, a vertical drive unit 22, a columnprocessing unit 23, a horizontal drive unit 24, a system control unit25, and the like.

The light receiving element 1 is further provided with a signalprocessing unit 26 and a data storage unit 27. Note that the signalprocessing unit 26 and the data storage unit 27 may be mounted on thesame substrate as that of the light receiving element 1, and may bedisposed on a substrate in a module different from that the lightreceiving element 1.

The pixel array portion 21 generates charge corresponding to the amountof received light, and is configured such that pixels 10 outputtingsignals corresponding to the charge are disposed in a two-dimensionalmatrix in a row direction and a column direction. That is, the pixelarray portion 21 performs photoelectric conversion of incident light andincludes a plurality of pixels 10 that output signals corresponding tocharge obtained as a result of the photoelectric conversion. Here, therow direction is a direction in which the pixels 10 are arranged in thehorizontal direction, and the column direction is a direction in whichthe pixels 10 are arranged in the vertical direction. The row directionis a transverse direction in the drawing, and the column direction is alongitudinal direction in the drawing. Details of the pixel 10 will bedescribed later in FIG. 2 and the subsequent drawings.

In the pixel array portion 21, a pixel drive line 28 is wired in the rowdirection for each pixel row and two vertical signal lines 29 are wiredin the column direction for each pixel column in a pixel array having amatrix form. The pixel drive line 28 transmits a drive signal forperforming driving at the time of reading out a signal from the pixel10. Note that, in FIG. 1 , one wiring is illustrated for the pixel driveline 28, but the number of wirings is not limited to one. One end of thepixel drive line 28 is connected to an output end corresponding to eachrow of the vertical drive unit 22.

The vertical drive unit 22, which is constituted by a shift register, anaddress decoder, or the like, drives all of the pixels 10 of the pixelarray portion 21 at the same time, in units of rows, or the like. Thatis, the vertical drive unit 22 constitute a drive unit that controls anoperation of each unit pixel 10 of the pixel array portion 21 along withthe system control unit 25 controlling the vertical drive unit 22.

A detection signal which is output from each pixel 10 of a pixel row inaccordance with driving control of the vertical drive unit 22 is inputto the column processing unit 23 through the vertical signal line 29.The column processing unit 23 performs predetermined signal processingon a detection signal which is output from each pixel 10 through thevertical signal line 29, and temporarily holds the detection signalhaving been subjected to the signal processing. The column processingunit 23 specifically performs noise removal processing, analog todigital (AD) conversion processing, or the like as signal processing.

The horizontal drive unit 24 is constituted by a shift register, anaddress decoder, or the like and sequentially selects unit circuitscorresponding to the pixel columns of the column processing unit 23.Through selective scanning of the horizontal drive unit 24, detectionsignals subjected to the signal processing for each unit circuit in thecolumn processing unit 23 are sequentially output to the signalprocessing unit 26.

The system control unit 25, which is constituted by a timing generatorfor generating various timing signals, or the like, performs drivingcontrol of the vertical drive unit 22, the column processing unit 23,the horizontal drive unit 24, and the like on the basis of the varioustiming signals generated by the timing generator.

The signal processing unit 26 has at least a calculation processingfunction and performs various signal processing such as calculationprocessing on the basis of a detection signal which is output from thecolumn processing unit 23. The data storage unit 27 temporarily storesdata required for signal processing performed by the signal processingunit 26 when performing the signal processing.

The light receiving element 1 configured as described above outputs adepth image in which information on a distance to an object is stored inpixel values as a depth value.

<2. Cross-Sectional View According to First Configuration Example ofPixel>

FIG. 2 is a cross-sectional view illustrating a first configurationexample of the pixels 10 disposed in the pixel array portion 21.

The light receiving element 1 includes a semiconductor substrate 41 anda multi-layered wiring layer 42 formed on the surface side (the lowerside in the drawing) of the semiconductor substrate 41.

The semiconductor substrate 41 is formed of, for example, silicon (Si)and is formed to have a thickness of, for example, approximately severalμm. In the semiconductor substrate 41, for example, N-type (secondconductive type) semiconductor regions 52 are formed in units of pixelsin a P-type (first conductive type) semiconductor region 51, and thusphotodiodes PD are formed in units of pixels. The P-type semiconductorregion 51 provided on both the surface and the rear surface of thesemiconductor substrate 41 also serves as a hole charge storage regionfor suppressing a dark current.

The upper surface of the semiconductor substrate 41 which is on theupper side in FIG. 2 is the rear surface of the semiconductor substrate41 and is a light incident surface on which light is incident. Anantireflection film 43 is formed on the upper surface of thesemiconductor substrate 41 on the rear surface side.

The antireflection film 43 has a laminated structure in which, forexample, a fixed charge film and an oxide film are laminated, and forexample, an insulated thin film having a high dielectric constant(High-k) according to an atomic layer deposition (ALD) method may beused. Specifically, hafnium oxide (HfO₂), aluminum oxide (Al₂O₃),titanium oxide (TiO₂), strontium titan oxide (STO), and the like can beused. In the example of FIG. 2 , the antireflection film 43 isconfigured such that a hafnium oxide film 53, an aluminum oxide film 54,and a silicon oxide film 55 are laminated.

An inter-pixel light shielding film 45 that prevents incident light frombeing incident on adjacent pixels is formed on the upper surface of theantireflection film 43 and at a boundary portion 44 of the pixel 10adjacent to the semiconductor substrate 41 (hereinafter also referred toas a pixel boundary portion 44). A material of the inter-pixel lightshielding film 45 may be a material that shields light, and examples ofthe material may include metal materials such as tungsten (W), aluminum(Al), and copper (Cu).

A flattening film 46 is constituted by an insulating film of such assilicon oxide (SiO₂), silicon nitride (SiN), silicon oxynitride (SiON),or an organic material such as a resin on the upper surface of theantireflection film 43 and the upper surface of the inter-pixel lightshielding film 45.

Then, an on-chip lens 47 is formed on the upper surface of theflattening film 46 in units of pixels. The on-chip lens 47 is formed ofa resin material such as a styrene-based resin, an acrylic-based resin,a styrene-acrylic copolymer resin, or a siloxane-based resin. Lightcollected by the on-chip lens 47 is efficiently incident on a photodiodePD.

In addition, an inter-pixel separation portion 61 that separatesadjacent pixels is formed from the rear surface side (on-chip lens 47side) of the semiconductor substrate 41 to a predetermined depth in asubstrate depth direction at the pixel boundary portion 44 on the rearsurface side of the semiconductor substrate 41. An outer circumferenceportion including a bottom surface and a side wall of the inter-pixelseparation portion 61 is covered with the hafnium oxide film 53 which isa portion of the antireflection film 43. The inter-pixel separationportion 61 prevents incident light from penetrating the next pixel 10and being confined in its own pixel, and prevent leakage of incidentlight from the adjacent pixel 10.

In the example of FIG. 2 , the silicon oxide film 55 and the inter-pixelseparation portion 61 are formed at the same time by embedding thesilicon oxide film 55, which is a material of an uppermost layer of theantireflection film 43, in a trench (groove) dug from the rear surfaceside, and thus the silicon oxide film 55 which is a portion of thelaminated film as the antireflection film 43 and the inter-pixelseparation portion 61 are formed of the same material but theirmaterials do not necessarily need to be the same. The material embeddedin the trench (groove) dug from the rear surface side as the inter-pixelseparation portion 61 may be a metal material such as tungsten (W),aluminum (Al), titanium (Ti), or titanium nitride (TiN).

On the other hand, two transfer transistors TRG1 and TRG2 are formed forone photodiode PD formed in each pixel 10 on the surface side of thesemiconductor substrate 41 on which the multi-layered wiring layer 42 isformed. In addition, floating diffusion regions FD1 and FD2 as chargeaccumulation portions for temporarily holding charge transferred fromthe photodiode PD are constituted by a high-concentration N-typesemiconductor region (N-type diffusion region) on the surface side ofthe semiconductor substrate 41.

The multi-layered wiring layer 42 is constituted by a plurality of metalfilms M and an insulating interlayer film 62 therebetween. In FIG. 2 ,an example in which the multi-layered wiring layer 42 is constituted bythree layers of a first metal film M1 to a third metal film M3 isillustrated.

A reflection film (reflection member) 63 is formed in a region which ispositioned below a region where the photodiode PD is formed in the firstmetal film M1 closest to the semiconductor substrate 41, among theplurality of metal films M of the multi-layered wiring layer 42, thatis, in a region of which at least a portion overlaps the region wherethe photodiode PD is formed when seen in a plan view. The reflectionfilm 63 is formed of the same material as those of the other metalwirings 67 of the first metal film M1, for example, a metal film such ascopper (Cu), aluminum (Al), tungsten (W), titanium (Ti), or titaniumnitride (TiN).

The reflection film 63 has a function of making infrared rays, incidentinto the semiconductor substrate 41 from a light incident surfacethrough the on-chip lens 47 and having passed through the semiconductorsubstrate 41 without being subjected to photoelectric conversion in thesemiconductor substrate 41, be reflected at the reflection film 63 andincident into the semiconductor substrate 41 again. By such a reflectionfunction, it is possible to increase the amount of infrared rayssubjected to photoelectric conversion in the semiconductor substrate 41and improve quantum efficiency (QE), that is, the sensitivity of thepixel 10 for infrared rays.

In addition, the reflection film 63 shields infrared rays, incident intothe semiconductor substrate 41 from a light incident surface through theon-chip lens 47 and having passed through the semiconductor substrate 41without being subjected to photoelectric conversion in the semiconductorsubstrate 41, by the first metal film M1 closest to the semiconductorsubstrate 41 and prevents the infrared rays from passing through asecond metal film M2 and a third metal film M3 positioned below thefirst metal film M1. Thus, the reflection film 63 can also be referredto as a light shielding film. By such a light shielding function, it ispossible to prevent infrared rays, having passed through thesemiconductor substrate 41 without being subjected to photoelectricconversion in the semiconductor substrate 41, from being dispersed bythe metal film M below the first metal film M1 and being incident onsurrounding pixels. Thereby, it is possible to prevent light from beingdetected erroneously in the surrounding pixels.

In addition, an inter-pixel light shielding unit 65 that preventsincident light, which is reflected by the reflection film 63, from beingincident on the photodiode PD of the next pixel 10 is formed at thepixel boundary portion 44 of the multi-layered wiring layer 42. As thematerial of the inter-pixel light shielding unit 65, for example, thesame material as that of the metal wiring 67 of the first metal film M1including the reflection film 63 may be used. In addition, for example,when the metal wiring 67 is copper, a material different from that ofthe metal wiring 67 of the first metal film M1 may be used as thematerial of the inter-pixel light shielding unit 65 by using tungsten asthe material or constituting the inter-pixel light shielding unit 65 byan infrared absorption film using an organic material, or the like.

The position of the inter-pixel light shielding unit 65 in a substratedepth direction is above (semiconductor substrate 41 side) thereflection film 63 of the first metal film M1 in order to accomplish thepurpose of the inter-pixel light shielding unit 65. For example, theinter-pixel light shielding unit 65 is formed at the same position(position in a depth direction) as a layer of a gate contact 66 thatconnects a gate of the transfer transistor TRG1 or TRG2 formed ofpolysilicon or the like and the metal wiring 67 of the first metal filmM1, or is formed on a side closer to the semiconductor substrate 41. Ina case where the inter-pixel light shielding unit 65 is formed at thesame position as the layer of the gate contact 66, the inter-pixel lightshielding unit 65 and the gate contact 66 can be formed at the sametime, and thus it is possible to share operations and reduce the numberof steps.

Note that a metal wiring which is electrically connected to the gate ofthe transfer transistor TRG1 or TRG2 through the gate contact 66 amongthe metal wirings 67 of the first metal film M1 is referred to as acontact wiring 67.

A wiring capacitance 64 is formed in, for example, the second metal filmM2, which is a predetermined metal film M among the plurality of metalfilms M of the multi-layered wiring layer 42, by forming a pattern, forexample, in a comb tooth shape. The reflection film 63 and the wiringcapacitance 64 may be formed in the same layer (metal film M), but in acase where they are formed in different layers, the wiring capacitance64 is formed in a layer farther from the semiconductor substrate 41 thanthe reflection film 63. In other words, the reflection film 63 is formedto be closer to the semiconductor substrate 41 than the wiringcapacitance 64 is.

As described above, the light receiving element 1 has a rear surfaceirradiation type structure in which the semiconductor substrate 41 whichis a semiconductor layer is disposed between the on-chip lens 47 and themulti-layered wiring layer 42, and incident light is incident on thephotodiode PD from the rear surface side where the on-chip lens 47 isformed.

In addition, the pixel 10 includes two transfer transistors TRG1 andTRG2 for the photodiode PD provided in each pixel, and is configured tobe able to distribute charge (electrons) generated by being subjected tophotoelectric conversion in the photodiode PD to the floating diffusionregion FD1 or FD2.

Reflected light received by the light receiving element 1, which isinfrared rays having a wavelength of approximately 780 nm to 1000 nm, isless absorbed by silicon of the semiconductor substrate 41 and has lowquantum efficiency. For this reason, in the pixel 10 according to thefirst configuration example, the inter-pixel separation portion 61 isformed in the pixel boundary portion 44 to prevent incident light frompenetrating the next pixel 10 and being confined in its own pixel, andprevent leakage of incident light from the adjacent pixel 10. Inaddition, by providing the reflection film 63 in a metal film M belowthe region where the photodiode PD is formed, infrared rays which havepassed through the semiconductor substrate 41 without being subjected tophotoelectric conversion in the semiconductor substrate 41 are reflectedby the reflection film 63, and the infrared rays are made to be incidentinto the semiconductor substrate 41 again.

On the other hand, the reflection film 63 is provided in the first metalfilm M1 below the region where the photodiode PD is formed, and thusthere is a concern that incident light reflected by the reflection film63 may penetrate an adjacent pixel, for example, as indicated by anarrow in FIG. 3 . Consequently, the inter-pixel light shielding unit 65is formed in the pixel boundary portion 44 of the multi-layered wiringlayer 42 to prevent leakage of incident light to an adjacent pixel dueto wraparound from the multi-layered wiring layer 42.

With the above-described configuration, it is possible to increase theamount of infrared rays subjected to photoelectric conversion in thesemiconductor substrate 41 and improve quantum efficiency (QE), that is,the sensitivity of the pixel 10 for infrared rays.

<3. Modification Example of First Configuration Example>

FIG. 4 is a cross-sectional view illustrating a modification example ofthe pixel 10 according to the first configuration example illustrated inFIG. 2 .

In FIG. 4 , portions corresponding to those in the first configurationexample illustrated in FIG. 2 are denoted by the same reference numeralsand signs, and description of the portions will be appropriatelyomitted.

The modification example of FIG. 4 is different from the firstconfiguration example of FIG. 2 in that the inter-pixel separationportion 61, which is a deep trench isolation (DTI) formed by being dugfrom the rear surface side (on-chip lens 47 side) of the semiconductorsubstrate 41, is replaced with an inter-pixel separation portion 71penetrating the semiconductor substrate 41, and the other respects arecommon to the modification example and the first configuration example.

The inter-pixel separation portion 71 is formed by forming a trench topenetrate a portion ranging from the rear surface side (on-chip lens 47side) or the surface side of the semiconductor substrate 41 to thesubstrate surface on the opposite side and embedding the silicon oxidefilm 55, which is a material of the uppermost layer of theantireflection film 43, in the trench. Examples of a material to beembedded in the trench as the inter-pixel separation portion 71 includemetal materials such as tungsten (W), aluminum (Al), titanium (Ti), andtitanium nitride (TiN), in addition to an insulating film such as thesilicon oxide film 55.

Adjacent pixels can be completely electrically separated from each otherby forming such an inter-pixel separation portion 71. Thereby, incidentlight is prevented from penetrating the next pixel 10 and being confinedin its own pixel, and leakage of incident light from the adjacent pixel10 is prevented. In addition, the inter-pixel light shielding unit 65 isformed at the pixel boundary portion 44 of the multi-layered wiringlayer 42 to prevent incident light from leaking to an adjacent pixel dueto wraparound from the multi-layered wiring layer 42.

Thus, also in the modification example of the first configurationexample, it is possible to increase the amount of infrared rays beingsubjected to photoelectric conversion in the semiconductor substrate 41to improve quantum efficiency, that is, the sensitivity of the pixel 10for infrared rays.

<4. Circuit Configuration Example of Pixel>

FIG. 5 illustrates a circuit configuration of the pixel 10 which istwo-dimensionally disposed in the pixel array portion 21.

The pixel 10 includes the photodiode PD as a photoelectric conversionelement. In addition, the pixel 10 includes two transfer transistorsTRG, two floating diffusion regions FD, two additional capacitors FDL,two switching transistors FDG, two amplification transistors AMP, tworeset transistors RST, and two selection transistors SEL. Further, thepixel 10 includes a charge discharging transistor OFG.

Here, in a case where the two transfer transistors TRG, the two floatingdiffusion regions FD, the two additional capacitors FDL, the twoswitching transistors FDG, the two amplification transistors AMP, thetwo reset transistors RST, and the two selection transistors SEL whichare provided in the pixel 10 are distinguished from each other, they arerespectively referred to as transfer transistors TRG1 and TRG2, floatingdiffusion regions FD1 and FD2, additional capacitors FDL1 and FDL2,switching transistors FDG1 and FDG2, amplification transistors AMP1 andAMP2, reset transistors RST1 and RST2, and selection transistors SEL1and SEL2 as illustrated in FIG. 5 .

The transfer transistor TRG, the switching transistor FDG, theamplification transistor AMP, the selection transistor SEL, the resettransistor RST, and the charge discharging transistor OFG areconstituted by, for example, an N-type MOS transistor.

The transfer transistor TRG1 is set to be in an electrical conductionstate in response to a transfer drive signal TRG1 g when the transferdrive signal TRG1 g supplied to a gate electrode is set to be in anactive state, and thus the transfer transistor TRG1 transfers chargeaccumulated in the photodiode PD to the floating diffusion region FD1.The transfer transistor TRG2 is set to be in an electrical conductionstate in response to a transfer drive signal TRG2 g when the transferdrive signal TRG2 g supplied to a gate electrode is set to be an activestate, and thus the transfer transistor transfers charge accumulated inthe photodiode PD to the floating diffusion region FD2.

The floating diffusion regions FD1 and FD2 are charge accumulationportions that temporarily hold charge transferred from the photodiodePD.

The switching transistor FDG1 is set to be in an electrical conductionstate in response to an FD drive signal FDG1 g when the FD drive signalFDG1 g supplied to a gate electrode is set to be in an active state, andthus the switching transistor FDG1 connects the additional capacitorFDL1 to the floating diffusion region FD1. The switching transistor FDG2is set to be in an electrical conduction state in response to an FDdrive signal FDG2 g when the FD drive signal FDG2 g supplied to a gateelectrode is set to be in an active state, and thus the switchingtransistor FDG2 connects the additional capacitor FDL2 to the floatingdiffusion region FD2. The additional capacitors FDL1 and FDL2 areconstituted by the wiring capacitance 64 in FIG. 2 .

The reset transistor RST1 resets the potential of the floating diffusionregion FD1 by being set to be in an electrical conduction state inresponse to a reset drive signal RSTg when the reset drive signal RSTgsupplied to a gate electrode is set to be in an active state. The resettransistor RST2 resets the potential of the floating diffusion regionFD2 by being set to be in an electrical conduction state in response toa reset drive signal RSTg when the reset drive signal RSTg supplied to agate electrode is set to be in an active state. Note that, when thereset transistors RST1 and RST2 are set to be in an active state, theswitching transistors FDG1 and FDG2 are also set to be in an activestate at the same time, and the additional capacitors FDL1 and FDL2 arealso reset.

The vertical drive unit 22 sets the switching transistors FDG1 and FDG2to be in an active state, for example, in the case of high illuminancewith a large amount of incident light to connect the floating diffusionregion FD1 and the additional capacitor FDL1 and connect the floatingdiffusion region FD2 and the additional capacitor FDL2. Accordingly, alarger amount of charges can be accumulated when the illuminance ishigh.

On the other hand, in the case of low illuminance with a small amount ofincident light, the vertical drive unit 22 sets the switchingtransistors FDG1 and FDG2 to be in an inactive state to separate theadditional capacitors FDL1 and FDL2 from the floating diffusion regionsFD1 and FD2. Accordingly, conversion efficiency can be improved.

The charge discharging transistor OFG discharges charge accumulated inthe photodiode PD by being set to be in an electrical conduction statein response to a discharge drive signal OFG1 g when the discharge drivesignal OFG1 g supplied to a gate electrode is set to be in an activestate.

The amplification transistor AMP1 is connected to a constant currentsource not illustrated in the drawing by a source electrode beingconnected to a vertical signal line 29A through the selection transistorSEL1, thereby constituting a source follower circuit. The amplificationtransistor AMP2 is connected to a constant current source notillustrated in the drawing by a source electrode being connected to avertical signal line 29B through the selection transistor SEL2, therebyconstituting a source follower circuit.

The selection transistor SEL1 is connected between the source electrodeof the amplification transistor AMP1 and the vertical signal line 29A.The selection transistor SEL1 is set to be in an electrical conductionstate in response to a selection signal SEL1 g when the selection signalSEL1 g supplied to a gate electrode is set to be in an active state, andoutputs a detection signal VSL1 output from the amplification transistorAMP1 to the vertical signal line 29A.

The selection transistor SEL2 is connected between the source electrodeof the amplification transistor AMP2 and the vertical signal line 29B.The selection transistor SEL2 is set to be in an electrical conductionstate in response to a selection signal SEL2 g when the selection signalSEL2 g supplied to a gate electrode is set to be in an active state, andoutputs a detection signal VSL2 output from the amplification transistorAMP2 to the vertical signal line 29B.

The transfer transistors TRG1 and TRG2, the switching transistors FDG1and FDG2, the amplification transistors AMP1 and AMP2, the selectiontransistors SEL1 and SEL2, and the charge discharging transistor OFG ofthe pixel 10 are controlled by the vertical drive unit 22.

In a pixel circuit of FIG. 5 , the additional capacitors FDL1 and FDL2and the switching transistors FDG1 and FDG2 controlling the connectionthereof may be omitted, but a high dynamic range can be secured byproviding an additional capacitor FDL and using it appropriatelyaccording to the amount of incident light.

Operations of the pixel 10 will be briefly described.

First, a reset operation for resetting charge in the pixel 10 isperformed in all pixels before light reception is started. That is, thecharge discharging transistor OFG, the reset transistors RST1 and RST2,and the switching transistors FDG1 and FDG2 are turned on, and chargeaccumulated in the photodiode PD, the floating diffusion regions FD1 andFD2, and the additional capacitors FDL1 and FDL2 is discharged.

After the accumulated charge is discharged, light reception is startedin all pixels.

In a light receiving period, the transfer transistors TRG1 and TRG2 arealternately driven. That is, in a first period, control for turning onthe transfer transistor TRG1 and turning off the transfer transistorTRG2 is performed. In the first period, charge generated in thephotodiode PD is transferred to the floating diffusion region FD1. In asecond period subsequent to the first period, control for turning offthe transfer transistor TRG1 and turning on the transfer transistor TRG2is performed. In the second period, charge generated in the photodiodePD is transferred to the floating diffusion region FD2. Thereby, chargegenerated in the photodiode PD is distributed to the floating diffusionregions FD1 and FD2 and accumulated.

Here, the transfer transistor TRG and the floating diffusion region FDwhere charge (electrons) obtained by photoelectric conversion is readare also referred to as active taps. In contrast, the transfertransistor TRG and the floating diffusion region FD where chargeobtained by photoelectric conversion is not read are also referred to asinactive taps.

In addition, when the light receiving period ends, the pixels 10 of thepixel array portion 21 are line-sequentially selected. In the selectedpixel 10, selection transistors SEL1 and SEL2 are turned on. Thereby,charge accumulated in the floating diffusion region FD1 is output to thecolumn processing unit 23 through the vertical signal line 29A as adetection signal VSL1. Charge accumulated in the floating diffusionregion FD2 is output to the column processing unit 23 through thevertical signal line 29B as a detection signal VSL2.

As described above, one light receiving operation is terminated, and thenext light receiving operation starting from a reset operation isexecuted.

Reflected light received by the pixel 10 is delayed in accordance with adistance to an object from a timing when a light source emits light. Adistribution ratio of charge accumulated in the two floating diffusionregions FD1 and FD2 changes depending on a delay time according to thedistance to the object, and thus the distance to the object can beobtained from the distribution ratio of charge accumulated in the twofloating diffusion regions FD1 and FD2.

<5. Plan View of Pixel>

FIG. 6 is a plan view illustrating an example of arrangement of a pixelcircuit illustrated in FIG. 5 .

A transverse direction in FIG. 6 corresponds to a row direction(horizontal direction) in FIG. 1 , and a longitudinal directioncorresponds to a column direction (vertical direction) in FIG. 1 .

As illustrated in FIG. 6 , the photodiode PD is constituted by an N-typesemiconductor region 52 in a central region of a rectangular pixel 10.

The transfer transistor TRG1, the switching transistor FDG1, the resettransistor RST1, the amplification transistor AMP1, and the selectiontransistor SEL1 are linearly disposed to be lined up on the outer sideof the photodiode PD and along one predetermined side among four sidesof the rectangular pixel 10, and the transfer transistor TRG2, theswitching transistor FDG2, the reset transistor RST2, the amplificationtransistor AMP2, and the selection transistor SEL2 are linearly disposedto be lined up along another side among the four sides of therectangular pixel 10.

Further, the charge discharging transistor OFG is disposed at a sidedifferent from the two sides of the pixel 10 where the transfertransistor TRG, the switching transistor FDG, the reset transistor RST,the amplification transistor AMP, and the selection transistor SEL areformed.

The inter-pixel light shielding unit 65 is configured, for example, bydisposing light shielding members having the same size and planar shapeas those of the gate contact 66 on boundary lines of the pixels 10 atpredetermined intervals. In the example of FIG. 6 , the planar shape ofone light shielding member constituting the inter-pixel light shieldingunit 65 is a rectangular shape, but may be a rectangular shape withrounded corners, an elliptical shape, or a circular shape.

FIGS. 7 and 8 are diagrams illustrating other examples of formation ofthe inter-pixel light shielding unit 65.

As illustrated in FIG. 7 , the inter-pixel light shielding unit 65 maybe configured such that the linear light shielding members having aplanar shape long in the direction of the boundary line of the pixel 10and short in the direction adjacent to other pixels 10 are disposed onthe boundary lines of the pixels 10 at predetermined intervals.

Alternatively, as illustrated in FIG. 8 , the inter-pixel lightshielding unit 65 may be configured such that the light shieldingmembers are disposed on the boundary lines of the pixels 10 so as tosurround the entire circumference of the pixels 10.

<6. Other Circuit Configuration Examples of Pixel>

FIG. 9 illustrates other circuit configuration examples of the pixel 10.

In FIG. 9 , portions corresponding to those in FIG. 5 are denoted by thesame reference signs, and description of the portions will beappropriately omitted.

The pixel 10 includes a photodiode PD as a photoelectric conversionelement. In addition, the pixel 10 includes two first transfertransistors TRGa, two second transfer transistors TRGb, two memoriesMEM, two floating diffusion regions FD, two reset transistors RST, twoamplification transistors AMP, and two selection transistors SEL.

Here, in a case where the two first transfer transistors TRGa, the twosecond transfer transistors TRGb, the two memories MEM, the two floatingdiffusion regions FD, the two reset transistors RST, the twoamplification transistors AMP, and the two selection transistors SELwhich are provided in the pixel 10 are distinguished from each other,they are respectively referred to as first transfer transistors TRGa1and TRGa2, second transfer transistors TRGb1 and TRGb2, transfertransistors TRG1 and TRG2, memories MEM1 and MEM2, floating diffusionregions FD1 and FD2, amplification transistors AMP1 and AMP2, andselection transistors SEL1 and SEL2 as illustrated in FIG. 9 .

Thus, as compared with the pixel circuit in FIG. 5 and the pixel circuitin FIG. 9 , the transfer transistors TRG are changed to two types, thatis, a first transfer transistor TRGa and a second transfer transistorTRGb, and the memories MEM are added. In addition, the additionalcapacitor FDL and the switching transistor FDG are omitted.

The first transfer transistor TRGa, the second transfer transistor TRGb,the reset transistor RST, the amplification transistor AMP, andselection transistor SEL are constituted by, for example, an N-type MOStransistor.

In the pixel circuit illustrated in FIG. 5 , charge generated by thephotodiode PD is transferred to the floating diffusion regions FD1 andFD2 and is held therein. However, in the pixel circuit illustrated inFIG. 9 , charge is transferred to the memories MEM1 and MEM2 provided ascharge accumulation portions and is held therein.

That is, the first transfer transistor TRGa1 is set to be in anelectrical conduction state in response to a first transfer drive signalTRGa1 g when the first transfer drive signal TRGa1 g supplied to a gateelectrode is set to be an active state, and thus the first transfertransistor TRGa1 transfers charge accumulated in the photodiode PD tothe memory MEM1. The first transfer transistor TRGa2 is set to be in anelectrical conduction state in response to a first transfer drive signalTRGa2 g when the first transfer drive signal TRGa2 g supplied to a gateelectrode is set to be an active state, and thus the first transfertransistor TRGa2 transfers charge accumulated in the photodiode PD tothe memory MEM2.

In addition, the second transfer transistor TRGb1 is set to be in anelectrical conduction state in response to a second transfer drivesignal TRGb1 g when the second transfer drive signal TRGb1 g supplied toa gate electrode is set to be in an active state, and thus the secondtransfer transistor TRGb1 transfers charge accumulated in the memoryMEM1 to the floating diffusion region FD1. The second transfertransistor TRGb2 is set to be in an electrical conduction state inresponse to a second transfer drive signal TRGb2 g when the secondtransfer drive signal TRGb2 g supplied to a gate electrode is set to bean active state, and thus the second transfer transistor TRGb2 transferscharge accumulated in the memory MEM2 to the floating diffusion regionFD2.

The reset transistor RST1 is set to be in an electrical conduction statein response to a reset drive signal RST1 g when the reset drive signalRST1 g supplied to a gate electrode is set to be an active state, andthus the reset transistor RST1 resets the potential of the floatingdiffusion region FD1. The reset transistor RST2 is set to be in anelectrical conduction state in response to a reset drive signal RST2 gwhen the reset drive signal RST2 g supplied to a gate electrode is setto be an active state, and thus the reset transistor RST2 resets thepotential of the floating diffusion region FD2. Note that, when thereset transistors RST1 and RST2 are set to be in an active state, thesecond transfer transistors TRGb1 and TRGb2 are also set to be in anactive state at the same time, and the memories MEM1 and MEM2 are alsoreset.

In the pixel circuit illustrated in FIG. 5 , charge generated by thephotodiode PD is distributed to the memories MEM1 and MEM2 and isaccumulated. In addition, charge held in the memories MEM1 and MEM2 istransferred to the floating diffusion regions FD1 and FD2 at a timingwhen the charge is read, and is output from the pixels 10.

<7. Plan View of Pixel>

FIG. 10 is a plan view illustrating an example of arrangement of thepixel circuit illustrated in FIG. 9 .

A transverse direction in FIG. 10 corresponds to a row direction(horizontal direction) in FIG. 1 , and a longitudinal directioncorresponds to a column direction (vertical direction) in FIG. 1 .

As illustrated in FIG. 10 , the photodiode PD is constituted by anN-type semiconductor region 52 in a central region of a rectangularpixel 10.

The first transfer transistor TRGa1, the second transfer transistorTRGb1, the reset transistor RST1, the amplification transistor AMP1, andthe selection transistor SEL1 are linearly disposed to be lined up onthe outer side of the photodiode PD and along one predetermined sideamong four sides of the rectangular pixel 10, and the first transfertransistor TRGa2, the second transfer transistor TRGb2, the resettransistor RST2, the reset transistor RST2, the amplification transistorAMP2, and the selection transistor SEL2 are linearly disposed to belined up along another side among the four sides of the rectangularpixel 10. The memories MEM1 and MEM2 are constituted by, for example, anembedded N-type diffusion region.

As the inter-pixel light shielding unit 65, a configuration in whichlight shielding members having the same planar shape as that of the gatecontact 66 are disposed at equal intervals, illustrated in FIG. 6 , hasbeen adopted, but configurations illustrated in FIGS. 7 and 8 or otherconfigurations may be adopted.

Note that the arrangement of the pixel circuit is not limited to theexample illustrated in FIG. 6 or FIG. 10 , and other arrangements canalso be adopted.

<8. Cross-Sectional View According to Second Configuration Example ofPixel>

FIG. 11 is a cross-sectional view illustrating a second configurationexample of the pixel 10.

In FIG. 11 , portions corresponding to those in the first configurationexample illustrated in FIG. 2 are denoted by the same reference numeralsand signs, and description of the portions will be appropriatelyomitted.

In the second configuration example of FIG. 11 , a moth eye structureportion 111 in which fine irregularities are periodically formed isformed on the rear surface of the semiconductor substrate 41 and above aregion where the photodiode PD is formed. In addition, theantireflection film 43 formed on the upper surface of a moth eyestructure portion 111 of the semiconductor substrate 41 is also formedto have a moth eye structure corresponding to the moth eye structureportion 111.

The moth eye structure portion 111 of the semiconductor substrate 41 isconfigured such that, for example, regions of a plurality ofquadrangular pyramids having substantially the same shape andsubstantially the same size are regularly provided (in a grid pattern).

The moth eye structure portion 111 is formed to have, for example, aninverted pyramid structure in which a plurality of regions having aquadrangular pyramid shape having vertices on the photodiode PD side arearranged to be lined up regularly.

Alternatively, the moth eye structure portion 111 may have a forwardpyramid structure in which regions of a plurality of quadrangularpyramids having vertices on the on-chip lens 47 side are arranged to belined up regularly. The sizes and arrangement of the plurality ofquadrangular pyramids may be formed randomly instead of being regularlyarranged. In addition, concave portions or convex portions of thequadrangular pyramids of the moth eye structure portion 111 have acertain degree of curvature and may have a rounded shape. The moth eyestructure portion 111 is only required to have a structure in which aconcave-convex structure is repeated periodically or randomly, and theshape of the concave portion or the convex portion is arbitrary.

FIG. 12 is a cross-sectional view illustrating another example offormation of the moth eye structure portion 111.

In the example of FIG. 12 , the shape of the moth eye structure portion111 has a surface parallel to the semiconductor substrate 41, and has aconcave-convex structure in which concave portions dug with a fixedamount in a depth direction of the substrate are arranged to be lined upat regular intervals. Note that, in FIG. 12 , the antireflection film 43is constituted by two layers, that is, the hafnium oxide film 53 and thesilicon oxide film 55, but may be constituted by three layers similar tothe other configuration examples or may be constituted by a singlelayer.

As in FIGS. 11 and 12 , the moth eye structure portion 111 is formed onthe light incident surface of the semiconductor substrate 41 as adiffraction structure that diffracts incident light, and thus it ispossible to alleviate a sudden change in a refractive index at aninterface of the substrate and reduce the influence of reflected light.

The other configurations of the second configuration example are thesame as those of the first configuration example.

Also in FIGS. 11 and 12 , the inter-pixel light shielding unit 65 isformed at the pixel boundary portion 44 of the multi-layered wiringlayer 42 to prevent leakage of incident light to an adjacent pixel dueto wraparound from the multi-layered wiring layer 42.

Thus, also in the second configuration example, it is possible tofurther increase the amount of infrared rays being subjected tophotoelectric conversion in the semiconductor substrate 41 to improvequantum efficiency, that is, the sensitivity of the pixel 10 forinfrared rays.

<9. Cross-Sectional View According to Third Configuration Example ofPixel>

FIG. 13 is a cross-sectional view illustrating a third configurationexample of the pixel 10.

In the above-described first and second configuration examples, aconfiguration in which leakage of incident light to an adjacent pixeldue to wraparound from the multi-layered wiring layer 42 is preventedhas been described, but in the third configuration example, aconfiguration in which leakage of incident light to an adjacent pixeldue to wraparound from the on-chip lens 47 side is prevented will bedescribed.

In FIG. 13 , portions corresponding to those in the first configurationexample illustrated in FIG. 2 are denoted by the same reference numeralsand signs, and description of the portions will be appropriatelyomitted.

In the third configuration example illustrated in FIG. 13 , thereflection film 63 formed at the same layer as that of the first metalfilm M1 below the region where the photodiode PD is formed in FIG. 2 ischanged to a reflection film 141. In addition, the inter-pixel lightshielding unit 65 formed at the pixel boundary portion 44 of themulti-layered wiring layer 42 in FIG. 2 is omitted.

A material for forming the reflection film 141 in the thirdconfiguration example is different from a material for forming thereflection film 63 in the first configuration example. Specifically, inthe first configuration example, the reflection film 141 is formed ofthe same material (for example, copper, aluminum, or the like) as thatof the metal wiring 67 which is electrically connected to the gate ofthe transfer transistor TRG1 or TRG2, but in the third configurationexample, the reflection film 141 may be formed of a material differentfrom that of the metal wiring 67. For example, in a case where the metalwiring 67 is formed of copper, the reflection film 141 is formed ofaluminum, tungsten (W), platinum (Pt), nickel (Ni), or the like.

A material for forming the reflection film 141 can be determined inaccordance with, for example, the thickness of the semiconductorsubstrate 41. For example, when the semiconductor substrate 41 has alarge thickness (for example, when the thickness is 6 μm or greater),aluminum can be adopted as the material of the reflection film 141. Inaddition, for example, when the semiconductor substrate 41 has a smallthickness (for example, when the thickness is less than 6 μm), tungsten,platinum, nickel, or the like can be adopted as the material of thereflection film 141.

In other words, for example, when the semiconductor substrate 41 has alarge thickness (for example, when the thickness is 6 μm or greater), amaterial having a relatively high reflectance (for example, a materialhaving a reflectance higher than 70%) can be adopted as the material ofthe reflection film 141. In addition, for example, when thesemiconductor substrate 41 has a small thickness (for example, when thethickness is less than 6 μm), a material having a relatively lowreflectance (for example, a material having a reflectance of 30% to 70%or less) can be adopted as the material of the reflection film 141.

As the material for forming the reflection film 141, a material having areflectance (refractive index) lower than those of the materials of theother metal wirings 67 of the first metal film M1 in at least awavelength range of infrared rays is used. Examples of such a materialinclude metals such as Al, Ni, Cr, Fe, Pt, Rh, and Sn, alloys thereof,metal compounds such as Ta₂O₅, Al₂O₃, and Si₃N₄, and the like.

The other configurations of the third configuration example are the sameas those of the first configuration example.

Reflected light received by the light receiving element 1 is infraredrays having a wavelength of approximately 780 nm to 1000 nm, and is lessabsorbed by silicon which is the semiconductor substrate 41 and has lowquantum efficiency. For this reason, light incident on the semiconductorsubstrate 41 penetrates the semiconductor substrate 41 and is reflectedby the reflection film 141 again toward the semiconductor substrate 41.In this case, when the reflectance of the reflection film 141 is as highas it is close to 100%, light reflected by the reflection film 141further penetrates the light incident surface of the semiconductorsubstrate 41, is reflected by the on-chip lens 47, and leaks into anadjacent pixel 10 as indicated by a solid arrow in FIG. 14 , which mayresult in flare.

According to the third configuration example, the reflection film 141 isformed of a material having a reflectance lower than those of thematerials of the other metal wirings 67 of the first metal film M1 andis formed to have a reflectance lower than those of the other metalwirings 67 in accordance with the thickness of the semiconductorsubstrate 41, and thus it is possible to perform adjustment so that alllight beams reflected by the reflection film 141 are absorbed in thesemiconductor substrate 41 as indicated by a dashed arrow in FIG. 14 .Thereby, light reflected by the reflection film 141 can be preventedfrom further penetrating the light incident surface of the semiconductorsubstrate 41, and thus it is possible to prevent leakage of incidentlight to an adjacent pixel due to wraparound from the on-chip lens 47side.

With the above-described configuration, it is possible to furtherincrease the amount of infrared rays being subjected to photoelectricconversion in the semiconductor substrate 41 to improve quantumefficiency, that is, the sensitivity of the pixel 10 for infrared rays,and to suppress the cause of flare due to reflected light penetratingthe semiconductor substrate 41.

<10. Modification Example of Third Configuration Example>

First Modification Example

FIG. 15 is a cross-sectional view illustrating a first modificationexample of the pixel 10 according to the third configuration exampleillustrated in FIG. 13 .

In FIG. 15 , portions corresponding to those in the third configurationexample illustrated in FIG. 13 are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

In the first modification example of FIG. 15 , the position of thereflection film 141 in the depth direction of the substrate is differentfrom that in the third configuration example illustrated in FIG. 13 ,and the other respects are common to the first modification exampleillustrated in FIG. 15 and the third configuration example illustratedin FIG. 13 .

Specifically, in the third configuration example illustrated in FIG. 13, the reflection film 141 is formed at the same position (the samelayer) as the first metal film M1 in the depth direction of thesubstrate, but the reflection film 141 is formed at a position (layer)different from that of the first metal film M1 in the first modificationexample of FIG. 15 . Specifically, the reflection film 141 is formed ona side closer to the photodiode PD (semiconductor substrate 41 side)than the first metal film M1 in the depth direction of the substrate.

In a case where the reflection film 141 is formed at the same layer asthe first metal film M1, the reflection film 141 has to be disposed toavoid the metal wirings 67 of the first metal film M1 as illustrated inA of FIG. 16 , and thus the area of the reflection film 141 when seen ina plan view is reduced.

On the other hand, in a case where the reflection film 141 is formed ata layer different from that of the first metal film M1, the metalwirings 67 of the first metal film M1 and the reflection film 141 do notinterfere with each other when seen in a plan view as illustrated in Bof FIG. 16 , and thus the reflection film 141 can be disposed in a largesize in a region overlapping the photodiode PD. Thereby, it is possibleto more greatly achieve the purpose of the reflection film 63. That is,a larger amount of infrared rays having passed through the semiconductorsubstrate 41 without being subjected to photoelectric conversion in thesemiconductor substrate 41 can be reflected by the reflection film 63 tobe incident into the semiconductor substrate 41.

With the above-described configuration, it is possible to furtherincrease the amount of infrared rays being subjected to photoelectricconversion in the semiconductor substrate 41 to improve quantumefficiency, that is, the sensitivity of the pixel 10 for infrared rays,and to suppress the cause of flare due to reflected light penetratingthe semiconductor substrate 41.

Second Modification Example

FIG. 17 is a cross-sectional view illustrating a second modificationexample of the pixel 10 according to the third configuration exampleillustrated in FIG. 13 .

In FIG. 17 , portions corresponding to those in the third configurationexample illustrated in FIG. 13 are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

In the second modification example illustrated in FIG. 17 , thereflection film 141 in the third configuration example illustrated inFIG. 13 is replaced with a reflection film 141P, and the otherconfigurations are common to the second modification example illustratedin FIG. 17 and the third configuration example illustrated in FIG. 13 .

The position of the reflection film 141P in a depth direction of thesubstrate is different from the position of the reflection film 141illustrated in FIG. 13 , and a material for forming the reflection film141P is also different from the material for forming the reflection film141.

Specifically, the reflection film 141P is formed of the same material(for example, polysilicon) as those of the gates of the transfertransistors TRG1 and TRG2 at the same depth position of the substrate asthose of the gates of the transfer transistors TRG1 and TRG2. Thereflection film 141P can be formed at the same time as when the gates ofthe transfer transistors TRG1 and TRG2 are formed by forming thereflection film 141P using the same material at the same depth positionof the substrate as those of the gates of the transfer transistors TRG1and TRG2, and thus it is possible to share operations and reduce thenumber of steps. Note that the reflection film 141P may be formed ofpolysilicon and a salicide film.

As in the first modification example of FIG. 15 and the secondmodification example of FIG. 17 , the reflection film 141 or 141P isformed on a side closer to the photodiode PD side than the first metalfilm M1 in the depth direction of the substrate, and thus it is alsopossible to prevent leakage of incident light to an adjacent pixel dueto wraparound from the multi-layered wiring layer 42.

<11. Cross-Sectional View According to Fourth Configuration Example ofPixel>

FIG. 18 is a cross-sectional view illustrating a fourth configurationexample of the pixel 10.

In FIG. 18 , portions corresponding to those in the third configurationexample illustrated in FIG. 13 are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

In the fourth configuration example of FIG. 18 , a moth eye structureportion 161 in which fine irregularities are periodically formed isfurther formed on a connection surface between the semiconductorsubstrate 41 below a region where the photodiode PD is formed and themulti-layered wiring layer 42. The moth eye structure portion 161 can beformed to have an inverted pyramid structure or a forward pyramidstructure, similar to the moth eye structure portion 111 described inFIG. 11 . Alternatively, the moth eye structure portion 161 may have aconcave-convex structure in which concave portions parallel to thesemiconductor substrate 41 are arranged to be lined up at regularintervals, as illustrated in FIG. 12 .

The other configurations of the fourth configuration example are thesame as those of the third configuration example illustrated in FIG. 13.

The moth eye structure portion 161 is formed at an interface between thesemiconductor substrate 41 below a region where the photodiode PD isformed and the multi-layered wiring layer 42, and thus light havingpenetrated the photodiode PD is diffused by the moth eye structureportion 111 and reaches the reflection film 141. Since reflection ofinfrared rays by the reflection film 141 is suppressed, it is possibleto prevent light reflected by the reflection film 141 from furtherpenetrating the light incident surface of the semiconductor substrate41. As a result, it is possible to prevent leakage of incident light toan adjacent pixel due to wraparound from the on-chip lens 47 side.

<12. Cross-Sectional View According to Fifth Configuration Example ofPixel>

FIG. 19 is a cross-sectional view illustrating a fifth configurationexample of the pixel 10.

In FIG. 19 , portions corresponding to those in the third configurationexample illustrated in FIG. 13 are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

In the fifth configuration example of FIG. 19 , the reflection film 141in the third configuration example illustrated in FIG. 13 is replacedwith a reflection film 141M. The other configurations in FIG. 19 are thesame as those in the third configuration example illustrated in FIG. 13.

The reflection film 141M is different from the reflection film 141 inthat the surface shape thereof on the semiconductor substrate 41 sidehas a moth eye structure in which fine irregularities are periodicallyformed. The surface shape of the reflection film 141M on thesemiconductor substrate 41 side is formed to have a moth eye structure,and thus light having penetrated the photodiode PD is diffused by thereflection film 141M and is reflected toward the semiconductor substrate41, similar to the fourth configuration example of FIG. 18 . Thereby,reflection of infrared rays by the reflection film 141M is suppressed,and thus it is possible to prevent light reflected by the reflectionfilm 141M from further penetrating the light incident surface of thesemiconductor substrate 41. As a result, it is possible to preventleakage of incident light to an adjacent pixel due to wraparound fromthe on-chip lens 47 side.

<13. Cross-Sectional View According to Sixth Configuration Example ofPixel>

FIG. 20 is a cross-sectional view illustrating a sixth configurationexample of the pixel 10.

In FIG. 20 , portions corresponding to those in the first to fifthconfiguration examples described above are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

The pixel 10 according to the fifth configuration example of FIG. 20includes the moth eye structure portion 111 on the rear surface of thesemiconductor substrate 41 and above the region where the photodiode PDis formed, and includes the moth eye structure portion 161 on the frontsurface of the semiconductor substrate 41 and below the region where thephotodiode PD is formed.

In addition, the pixel 10 according to a sixth configuration example ofFIG. 20 includes a reflection film 141 which is formed of a materialhaving a reflectance lower than those of the materials of the othermetal wirings 67 of the first metal film M1 in the layer of the firstmetal film M1 below the region where the photodiode PD is formed.

In other words, the pixel 10 according to the sixth configurationexample of FIG. 20 has a structure in which the moth eye structureportion 111 is added to the rear surface side of the semiconductorsubstrate 41 according to the fourth configuration example illustratedin FIG. 18 .

In the sixth configuration example of FIG. 20 , the shape of a fineconcave-convex structure of the moth eye structure portion 111 on therear surface side (upper side in the drawing) of the semiconductorsubstrate 41 and the shape of a fine concave-convex structure of themoth eye structure portion 161 on the front surface side (lower side inthe drawing) of the semiconductor substrate 41 may be the same ordifferent. In addition, the cycle of the concave-convex structure of themoth eye structure portion 111 and the cycle of the concave-convexstructure of the moth eye structure portion 161 may be the same ordifferent.

For example, in a case where the cycle of the concave-convex structureof the moth eye structure portion 111 is set to be longer than the cycleof the concave-convex structure of the moth eye structure portion 161,light having a wavelength close to infrared rays is diffused by the motheye structure portion 111, light having a wavelength close toultraviolet rays is diffused by the moth eye structure portion 161, andlight having a wavelength close to infrared rays is not diffused by themoth eye structure portion 161. In a case where the semiconductorsubstrate 41 has a large thickness and it is not necessary to relativelysuppress reflection of infrared rays, the cycle of the concave-convexstructure of the moth eye structure portion 111 is set to be longer thanthe cycle of the concave-convex structure of the moth eye structureportion 161. In contrast, in a case where the semiconductor substrate 41has a small thickness and the reflection of infrared rays in thereflection film 141 is desired to be suppressed, the cycle of theconcave-convex structure of the moth eye structure portion 161 is set tobe longer than the cycle of the concave-convex structure of the moth eyestructure portion 111.

Also in the sixth configuration example of FIG. 20 , it is possible toprevent leakage of incident light to an adjacent pixel due to wraparoundfrom the on-chip lens 47 side by the reflection film 141 having areflectance lower than those of the other metal wirings 67. In addition,it is possible to prevent light reflected by the reflection film 141from further penetrating the light incident surface of the semiconductorsubstrate 41 by the moth eye structure portions 111 and 161.

<14. Cross-Sectional View According to Seventh Configuration Example ofPixel>

FIG. 21 is a cross-sectional view illustrating a seventh configurationexample of the pixel 10.

In FIG. 21 , portions corresponding to those in the first to sixthconfiguration examples described above are denoted by the same referencesigns, and description of the portions will be appropriately omitted.

The pixel 10 according to the sixth configuration example of FIG. 21includes the moth eye structure portion 111 on the rear surface of thesemiconductor substrate 41.

In addition, the pixel 10 according to the sixth configuration exampleof FIG. 20 includes the reflection film 141 formed of a material havinga reflectance lower than those of the materials of the other metalwirings 67 of the first metal film M1 in the layer of the first metalfilm M1 below the region where the photodiode PD is formed.

In addition, a plurality of dummy contacts 181 are formed on the surfaceof the reflection film 141 on the semiconductor substrate 41 side. Thedummy contacts 181 are formed of the same material and in the same stepas that of the gate contact 66 connected to the gate of the transfertransistor TRG1 or TRG2, but are contact wirings that are not connectedto a gate of a pixel transistor. A fine concave-convex structure isformed by forming the plurality of dummy contacts 181 on the surface ofthe reflection film 141 on the semiconductor substrate 41 side, and thusthe same effects as those of the reflection film 141M in the fifthconfiguration example illustrated in FIG. 19 can be obtained.

That is, light having penetrated the photodiode PD is diffused by theplurality of dummy contacts 181 and is reflected toward thesemiconductor substrate 41 by the plurality of dummy contacts 181 formedon the surface of the reflection film 141M on the semiconductorsubstrate 41 side. Thereby, it is possible to prevent light reflected bythe reflection film 141 from further penetrating the light incidentsurface of the semiconductor substrate 41. As a result, it is possibleto prevent leakage of incident light to an adjacent pixel due towraparound from the on-chip lens 47 side.

Also in the seventh configuration example of FIG. 21 , it is possible toprevent leakage of incident light to an adjacent pixel due to wraparoundfrom the on-chip lens 47 side by the reflection film 141 having areflectance lower than those of the other metal wirings 67. In addition,it is possible to prevent light reflected by the reflection film 141from further penetrating the light incident surface of the semiconductorsubstrate 41 by the moth eye structure portion 111.

<Modification Example of Seventh Configuration Example>

Note that the planar shape and size of the dummy contact 181, the numberof dummy contacts 181 disposed on the plane of the reflection film 141,and the like are not particularly limited and can be determinedarbitrarily. The size and shape of the dummy contact 181 may be the sameas or different from the size and shape of the gate contact 66 connectedto the gate of the transfer transistor TRG1 or TRG2.

For example, as illustrated in FIG. 22 , the dummy contact 181 is formedto have a planar size larger than that of the gate contact 66, and maybe formed slightly above (photodiode PD side) the reflection film 141with the insulating interlayer film 62 interposed therebetween withoutbeing connected to the reflection film 141.

<15. Cross-Sectional View According to Eighth Configuration Example ofPixel>

FIG. 23 is a cross-sectional view illustrating an eighth configurationexample of the pixel 10.

In FIG. 23 , portions corresponding to those in the first to seventhconfiguration examples described above are denoted by the same referencenumerals and signs, and description of the portions will beappropriately omitted.

In the above-described first to seventh configuration examples and themodification examples thereof, various configurations in which leakageof incident light to an adjacent pixel due to wraparound from themulti-layered wiring layer 42 is prevented and various configurations inwhich leakage of incident light to an adjacent pixel due to wraparoundfrom the on-chip lens 47 side is prevented have been described. Byappropriately combining these various configurations, it is possible toadopt a configuration in which leakage of incident light to an adjacentpixel due to wraparound from the multi-layered wiring layer 42 and dueto wraparound from the on-chip lens 47 side is prevented.

For example, the pixel 10 according to the eighth configuration exampleillustrated in FIG. 23 has characteristic configurations of both thefirst configuration example illustrated in FIG. 2 and the thirdconfiguration example illustrated in FIG. 13 .

That is, the pixel 10 illustrated in FIG. 23 includes a reflection film141 formed of a material having a reflectance lower than those of thematerials of the other metal wirings 67 of the first metal film M1 inthe layer of the first metal film M1 below the region where thephotodiode PD is formed.

In addition, the pixel 10 illustrated in FIG. 23 includes an inter-pixellight shielding unit 65 that prevents incident light, which is reflectedby the reflection film 141, from being incident on the photodiode PD ofthe next pixel 10 at the pixel boundary portion 44 of the multi-layeredwiring layer 42.

Other configurations of the eighth configuration example of FIG. 23 ,for example, are the same as those of the first configuration exampleillustrated in FIG. 2 .

According to the pixel 10 illustrated in FIG. 23 which has theabove-described configuration, leakage of incident light to an adjacentpixel due to wraparound from the multi-layered wiring layer 42 isprevented by the inter-pixel light shielding unit 65 disposed at thepixel boundary portion 44 of the multi-layered wiring layer 42.

In addition, it is possible to prevent leakage of incident light to anadjacent pixel due to wraparound from the on-chip lens 47 side by thereflection film 141 disposed below the region where the photodiode PD isformed in the multi-layered wiring layer 42.

Further, for example, a pixel 10 illustrated in FIG. 24 has a structurein which the moth eye structure portion 111 is further added to the rearsurface of the semiconductor substrate 41, in addition to theinter-pixel light shielding unit 65 and the reflection film 141illustrated in FIG. 23 . It is possible to further suppress reflectionat an interface of the substrate by the moth eye structure portion 111.

Although not illustrated in the drawing, by appropriately combiningvarious configurations in which leakage of incident light to an adjacentpixel due to wraparound from the multi-layered wiring layer 42 isprevented (the above-described first and second configuration examples)and various configurations in which leakage of incident light to anadjacent pixel due to wraparound from the on-chip lens 47 side isprevented (the above-described third to seventh configuration examples),it is possible to simultaneously achieve the prevention of leakage ofincident light to an adjacent pixel due to wraparound from themulti-layered wiring layer 42 and the prevention of leakage of incidentlight to an adjacent pixel due to wraparound from the on-chip lens 47side.

<16. Cross-Sectional View According to Ninth Configuration Example ofPixel>

FIG. 25 is a cross-sectional view illustrating a ninth configurationexample of the pixel 10.

In FIG. 25 , portions corresponding to those in the above-describedfirst to eighth configuration examples are denoted by the same referencesigns, and description of the portions will be appropriately omitted.

In the above-described first to eighth configuration examples, the lightreceiving element 1 is configured using one semiconductor substrate,that is, only the semiconductor substrate 41, but in the ninthconfiguration example of FIG. 25 , the light receiving element 1 isconfigured using two semiconductor substrates, that is, thesemiconductor substrate 41 and the semiconductor substrate 301.

The pixel 10 according to the ninth configuration example of FIG. 25 isconfigured such that the eighth configuration example of FIG. 23 usingone semiconductor substrate 41 is changed to a configuration using twosemiconductor substrates, that is, the semiconductor substrate 41 andthe semiconductor substrate 301. Hereinafter, in order to facilitate theunderstanding, description will be given by also referring thesemiconductor substrate 41 and the semiconductor substrate 301 to as afirst substrate 41 and a second substrate 301, respectively.

The ninth configuration example of FIG. 25 is the same as the firstconfiguration example of FIG. 2 in that the inter-pixel light shieldingfilm 45, the flattening film 46, and the on-chip lens 47 are formed onthe light incident surface side of the first substrate 41. The ninthconfiguration example is also the same as the first configurationexample of FIG. 2 in that the inter-pixel separation portion 61 isformed at the pixel boundary portion 44 on the rear surface side of thefirst substrate 41.

In addition, the ninth configuration example is also the same as thefirst configuration example of FIG. 2 in that the photodiodes PD whichare photoelectric conversion units are formed on the first substrate 41in units of pixels and in that two transfer transistors TRG1 and TRG2and the floating diffusion regions FD1 and FD2 as charge accumulationportions are formed on the front surface side of the first substrate 41.

On the other hand, as a difference from the first configuration exampleof FIG. 2 , an insulating layer 313 of a wiring layer 311 which is thesurface side of the first substrate 41 is bonded to an insulating layer312 of the second substrate 301.

The wiring layer 311 of the first substrate 41 includes at least a metalfilm M of a single layer, and the reflection film 141 is formed in aregion positioned below the region where the photodiode PD is formed,using the metal film M. In addition, the inter-pixel light shieldingunit 65 is formed at the pixel boundary portion 44 of the wiring layer311.

pixel transistors Tr1 and Tr2 are formed at an interface on a sideopposite to the insulating layer 312 side which is a bonding surfaceside of the second substrate 301. The pixel transistors Tr1 and Tr2 are,for example, the amplification transistor AMP and the selectiontransistor SEL.

That is, in the first to eighth configuration examples configured usingonly one semiconductor substrate 41 (first substrate 41), all pixeltransistors of the transfer transistor TRG, the switching transistorFDG, the amplification transistor AMP, and the selection transistor SELare formed on the semiconductor substrate 41. However, in the lightreceiving element 1 according to the ninth configuration example whichis constituted by a laminated structure of two semiconductor substrates,pixel transistors other than the transfer transistor TRG, that is, theswitching transistor FDG, the amplification transistor AMP, and theselection transistor SEL are formed on the second substrate 301.

A multi-layered wiring layer 321 including at least metal films M of twolayers is formed on a side opposite to the first substrate 41 side ofthe second substrate 301. The multi-layered wiring layer 321 includes afirst metal film M11, a second metal film M12, and an insulatinginterlayer film 333.

A transfer drive signal TRG1 g that controls the transfer transistorTRG1 is supplied from the first metal film M11 of the second substrate301 to a gate electrode of the transfer transistor TRG1 of the firstsubstrate 41 by a through silicon via (TSV) 331-1 that penetrates thesecond substrate 301. A transfer drive signal TRG2 g that controls thetransfer transistor TRG2 is supplied from the first metal film M11 ofthe second substrate 301 to a gate electrode of the transfer transistorTRG2 of the first substrate 41 by a TSV 331-2 that penetrates the secondsubstrate 301.

Similarly, charge accumulated in the floating diffusion region FD1 istransferred from the first substrate 41 side to the first metal film M11of the second substrate 301 by a TSV 332-1 that penetrates the secondsubstrate 301. Charge accumulated in the floating diffusion region FD2is transferred from the first substrate 41 side to the first metal filmM11 of the second substrate 301 by a TSV 332-2 that penetrates thesecond substrate 301.

The wiring capacitance 64 is formed in a region, which is notillustrated in the drawing, of the first metal film M11 or the secondmetal film M12. The metal film M having the wiring capacitance 64 formedtherein is formed to have a high wiring density in order to form acapacity, and the metal film M connected to a gate electrode of thetransfer transistor TRG, the switching transistor FDG, or the like isformed to have a low wiring density in order to reduce an inducedcurrent. A configuration in which a wiring layer (metal film M)connected to the gate electrode is different for each pixel transistormay be adopted.

As described above, the pixel 10 according to the ninth configurationexample can be configured such that two semiconductor substrates, thatis, the first substrate 41 and the second substrate 301 are laminated,and the pixel transistors other than the transfer transistor TRG areformed on the second substrate 301 different from the first substrate 41including a photoelectric conversion unit. In addition, the verticaldrive unit 22 and the pixel drive line 28 that control the driving ofthe pixels 10, the vertical signal line 29 for transmitting a detectionsignal, and the like are also formed on the second substrate 301.Thereby, the pixel can be made fine, and the degree of freedom in backend of line (BEOL) design is also increased.

Also in the ninth configuration example, the reflection film 141 isformed in a region of the wiring layer 311 which is positioned below theregion where the photodiode PD is formed, and the inter-pixel lightshielding unit 65 is formed at the pixel boundary portion 44 of thewiring layer 311. Thereby, it is possible to simultaneously achieve theprevention of leakage of incident light to an adjacent pixel due towraparound from the multi-layered wiring layer 42 and the prevention ofleakage of incident light to an adjacent pixel due to wraparound fromthe on-chip lens 47 side.

The ninth configuration example of FIG. 25 is configured such that theeighth configuration example of FIG. 23 is changed to a laminatedstructure in which two semiconductor substrates are laminated. However,similarly, the above-described first to seventh configuration examplescan be changed to a laminated structure in which two semiconductorsubstrates are laminated.

<17. Configuration Example of IR Imaging Sensor>

The above-described pixel structure including at least one of theinter-pixel light shielding unit 65 and the reflection film 141 is notlimited to a light receiving element that outputs distance measurementinformation according to an indirect ToF scheme, and can also be appliedto an IR imaging sensor that receives infrared rays and generates an IRimage.

FIG. 26 illustrates a circuit configuration of the pixel 10 in a casewhere the light receiving element 1 is configured as an IR imagingsensor that generates and outputs an IR image.

In a case where the light receiving element 1 is a ToF sensor, the lightreceiving element 1 distributes charge generated by the photodiode PDinto two floating diffusion regions FD1 and FD2 and accumulates thecharge, and thus the pixel 10 includes two transfer transistors TRG, twofloating diffusion regions FD, two additional capacitors FDL, twoswitching transistors FDG, two amplification transistors AMP, two resettransistors RST, and two selection transistors SEL.

In a case where the light receiving element 1 is an IR imaging sensor,the number of charge accumulation portions in which charge generated bythe photodiode PD is temporarily held may be one, and thus the number oftransfer transistors TRG, the number of floating diffusion regions FD,the number of additional capacitors FDL, the number of switchingtransistors FDG, the number of amplification transistors AMP, the numberof reset transistors RST, and the number of selection transistors SELare also set to be one.

In other words, in a case where the light receiving element 1 is an IRimaging sensor, the pixel 10 is equivalent to a configuration in whichthe transfer transistor TRG2, the switching transistor FDG2, the resettransistor RST2, the amplification transistor AMP2, and the selectiontransistor SEL2 are omitted from the circuit configuration illustratedin FIG. 4 as illustrated in FIG. 26 . The floating diffusion region FD2and the vertical signal line 29B are also omitted.

FIG. 27 is a cross-sectional view of the pixel 10 in a case where thelight receiving element 1 is configured as an IR imaging sensor.

FIG. 27 illustrates a cross-sectional configuration in a case where theeighth configuration example illustrated in FIG. 23 is applied to an IRimaging sensor.

A difference between a case where the light receiving element 1 isconfigured as an IR imaging sensor and a case where the light receivingelement 1 is configured as a ToF sensor is whether the floatingdiffusion region FD2 formed on the front surface side of thesemiconductor substrate 41 and a pixel transistor are present or not, asdescribed in FIG. 26 . For this reason, a configuration of themulti-layered wiring layer 42 which is the front surface side of thesemiconductor substrate 41 is different from that in FIG. 23 .Specifically, as compared with FIG. 23 , the floating diffusion regionFD2 and the transfer transistor TRG2 are omitted in the pixel 10illustrated in FIG. 27 .

On the other hand, as a configuration which is common to FIG. 23 , inthe pixel 10 illustrated in FIG. 27 , the reflection film 141 is formedusing a material having a reflectance lower than those of the materialsof the other metal wirings 67 of the first metal film M1 in the layer ofthe first metal film M1 of the multi-layered wiring layer 42 below theregion where the photodiode PD is formed. In addition, the inter-pixellight shielding unit 65 is formed at the pixel boundary portion 44 ofthe multi-layered wiring layer 42.

FIG. 27 illustrates a cross-sectional configuration in a case where theeighth configuration example illustrated in FIG. 23 is applied to an IRimaging sensor. However, similarly, the above-described first to seventhconfiguration examples can be applied to an IR imaging sensor byomitting the floating diffusion region FD2 formed on the front surfaceside of the semiconductor substrate 41 and a pixel transistorcorresponding thereto.

Also in a case where the light receiving element 1 is configured as anIR imaging sensor, it is possible to prevent leakage of incident lightto an adjacent pixel due to wraparound from the multi-layered wiringlayer 42 by providing the inter-pixel light shielding unit 65 at thepixel boundary portion 44 of the multi-layered wiring layer 42. Further,it is possible to prevent leakage of incident light to an adjacent pixeldue to wraparound from the on-chip lens 47 side by providing thereflection film 141.

Thus, also in a case where the light receiving element 1 is configuredas an IR imaging sensor, it is possible to further increase the amountof infrared rays being subjected to photoelectric conversion in thesemiconductor substrate 41 to improve quantum efficiency, that is,sensitivity for infrared rays.

<18. Configuration Example of RGBIR Imaging Sensor>

The above-described pixel structure including at least one of theinter-pixel light shielding unit 65 and the reflection film 141 is notlimited to a light receiving element that receives only infrared rays,and can also be applied to an RGBIR imaging sensor that receivesinfrared rays and RGB rays.

FIG. 28 illustrates an example of arrangement of pixels in a case wherethe light receiving element 1 is configured as an RGBIR imaging sensorthat receives infrared rays and RGB rays.

In a case where the light receiving element 1 is configured as an RGBIRimaging sensor, an R pixel that receives light of R (red), a B pixelthat receives light of B (blue), a G pixel that receives light of G(green), and an IR pixel that receives light of IR (infrared) areallocated to 4 pixels of 2×2, as illustrated in A of FIG. 28 .

The reflection film 63 or 141 reflecting infrared rays which have passedthrough the semiconductor substrate 41 without being subjected tophotoelectric conversion in the semiconductor substrate 41 and makingthe infrared rays incident into the semiconductor substrate 41 again maybe disposed in all of the R pixel, the B pixel, the G pixel, and the IRpixel, or may be disposed in only some of the pixels for the purpose ofadjusting the amount of received light (light receiving sensitivity),and the like.

for example, as illustrated in B of FIG. 28 , a configuration in whichthe reflection film 63 or 141 is disposed in the IR pixel and the Rpixel and is not disposed in the B pixel and the G pixel among the Rpixel, the B pixel, the G pixel, and the IR pixel can be adopted.

<19. Configuration Example of Distance Measurement Module>

FIG. 29 is a block diagram illustrating a configuration example of adistance measurement module that outputs distance measurementinformation using the above-described light receiving element 1.

A distance measurement module 500 includes a light emission unit 511, alight emission control unit 512, and a light receiving unit 513.

The light emission unit 511 includes a light source that emits lighthaving a predetermined wavelength, and irradiates an object withirradiation light of which the brightness varies periodically. Forexample, the light emission unit 511 includes a light emitting diodethat emits infrared rays having a wavelength in a range of 780 nm to1000 nm as a light source, and generates irradiation light insynchronization with a light emission control signal CLKp of arectangular wave supplied from the light emission control unit 512.

Note that the light emission control signal CLKp is not limited to arectangular wave as long as it is a period signal. For example, thelight emission control signal CLKp may be a sine wave.

The light emission control unit 512 supplies the light emission controlsignal CLKp to the light emission unit 511 and the light receiving unit513 and controls an irradiation timing of irradiation light. Thefrequency of the light emission control signal CLKp is, for example, 20megahertz (MHz). Note that the frequency of the light emission controlsignal CLKp is not limited to 20 megahertz and may be 5 megahertz, 100megahertz, or the like.

The light receiving unit 513 receives reflected light reflected from anobject, calculates distance information for each pixel in accordancewith a result of light reception, and generates and outputs a depthimage in which a depth value corresponding to a distance to the object(subject) is stored as a pixel value.

The light receiving element 1 having the pixel structure of any one ofthe above-described first to eighth configuration examples is used inthe light receiving unit 513. For example, the light receiving element 1as the light receiving unit 513 calculates distance information for eachpixel from a detection signal corresponding to charge distributed to thefloating diffusion regions FD1 or FD2 of the pixels 10 of the pixelarray portion 21 on the basis of the light emission control signal CLKp.

As described above, as the light receiving unit 513 of the distancemeasurement module 500 that obtains and outputs information on adistance to a subject by an indirect ToF scheme, the light receivingelement 1 having the pixel structure of any one of the above-describedfirst to eighth configuration examples can be incorporated. Thereby, itis possible to improve distance measurement characteristics as thedistance measurement module 500.

<20. Configuration Example of Electronic Equipment>

Note that, as described above, the light receiving element 1 can beapplied to a distance measurement module, and can also be applied tovarious electronic equipment such as, for example, imaging devices suchas digital still cameras and digital video cameras equipped with adistance measurement function, and smartphones equipped with a distancemeasurement function.

FIG. 30 is a block diagram illustrating a configuration example of asmartphone as electronic equipment to which the present technology isapplied.

As illustrated in FIG. 30 , a smartphone 601 is configured such that adistance measurement module 602, an imaging device 603, a display 604, aspeaker 605, a microphone 606, a communication module 607, a sensor unit608, a touch panel 609, and a control unit 610 are connected to eachother via a bus 611. Further, the control unit 610 has functions as anapplication processing unit 621 and an operation system processing unit622 by causing a CPU to execute a program.

The distance measurement module 500 illustrated in FIG. 29 is applied tothe distance measurement module 602. For example, the distancemeasurement module 602 is disposed on the front surface of thesmartphone 601, and can output a depth value of a surface shape of theface, hand, finger, or the like of a user of the smartphone 601 as adistance measurement result by performing distance measurement on theuser.

The imaging device 603 is disposed on the front surface of thesmartphone 601, and acquires an image captured by the user of thesmartphone 601 by imaging the user as a subject. Note that, although notillustrated in the drawing, a configuration in which the imaging device603 is also disposed on the back surface of the smartphone 601 may beadopted.

The display 604 displays an operation screen for performing processingby the application processing unit 621 and the operation systemprocessing unit 622, an image captured by the imaging device 603, andthe like. The speaker 605 and the microphone 606 perform, for example,outputting of a voice of the other party and collecting of a user'svoice when making a call using the smartphone 601.

The communication module 607 performs network communication through acommunication network such as the Internet, a public telephone network,a wide area communication network for wireless mobiles such as aso-called 4G line and 5G line, a wide area network (WAN), and a localarea network (LAN), short-range wireless communication such as Bluetooth(registered trademark) and near field communication (NFC), and the like.The sensor unit 608 senses speed, acceleration, proximity, and the like,and the touch panel 609 acquires a user's touch operation on theoperation screen displayed on the display 604.

The application processing unit 621 performs processing for providingvarious services by the smartphone 601. For example, the applicationprocessing unit 621 can create a face by computer graphics thatvirtually reproduces the user's facial expression on the basis of adepth value supplied from the distance measurement module 602, and canperform processing for displaying the face on the display 604. Inaddition, the application processing unit 621 can perform processing ofcreating, for example, three-dimensional shape data of an arbitrarythree-dimensional object on the basis of a depth value supplied from thedistance measurement module 602.

The operation system processing unit 622 performs processing forrealizing basic functions and operations of the smartphone 601. Forexample, the operation system processing unit 622 can perform processingfor authenticating a user's face on the basis of a depth value suppliedfrom the distance measurement module 602, and unlocking the smartphone601. In addition, the operation system processing unit 622 can perform,for example, processing for recognizing a user's gesture on the basis ofa depth value supplied from the distance measurement module 602, and canperform processing for inputting various operations according to thegesture.

In the smartphone 601 configured in this manner, the above-describeddistance measurement module 500 is applied as the distance measurementmodule 602, and thus it is possible to perform, for example, processingfor measuring and displaying a distance to a predetermined object orcreating and displaying three-dimensional shape data of a predeterminedobject, and the like.

<21. Example of Application to Moving Body>

The technology according to the present disclosure (the presenttechnology) can be applied to various products. For example, thetechnology according to the present disclosure may be realized as adevice mounted on any type of moving body such as an automobile, anelectric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, apersonal mobility, an airplane, a drone, a ship, and a robot.

FIG. 31 is a block diagram illustrating a schematic configurationexample of a vehicle control system which is an example of a moving bodycontrol system to which the technology according to the presentdisclosure can be applied.

A vehicle control system 12000 includes a plurality of electroniccontrol units connected via a communication network 12001. In theexample illustrated in FIG. 31 , the vehicle control system 12000includes a drive system control unit 12010, a body system control unit12020, a vehicle exterior information detection unit 12030, a vehicleinterior information detection unit 12040, and an integrated controlunit 12050. Further, a microcomputer 12051, an audio/image output unit12052, and an in-vehicle network interface (I/F) 12053 are illustratedas a functional configuration of the integrated control unit 12050.

The drive system control unit 12010 controls operations of devicesrelated to a drive system of a vehicle according to various programs.For example, the drive system control unit 12010 functions as a drivingforce generator for generating a driving force of a vehicle such as aninternal combustion engine or a driving motor, a driving forcetransmission mechanism for transmitting a driving force to wheels, asteering mechanism for adjusting a turning angle of a vehicle, and acontrol device such as a braking device that generates a braking forceof a vehicle.

The body system control unit 12020 controls operations of variousdevices mounted in the vehicle body according to various programs. Forexample, the body system control unit 12020 functions as a controldevice of a keyless entry system, a smart key system, a power windowdevice, or various lamps such as a head lamp, a back lamp, a brake lamp,a turn signal, or a fog lamp. In this case, radio waves transmitted froma portable device that substitutes for a key or signals of variousswitches can be input to the body system control unit 12020. The bodysystem control unit 12020 receives input of these radio waves or signalsand controls a door lock device, a power window device, a lamp, and thelike of the vehicle.

The vehicle exterior information detection unit 12030 detectsinformation on the exterior of the vehicle in which the vehicle controlsystem 12000 is mounted. For example, an imaging unit 12031 is connectedto the vehicle exterior information detection unit 12030. The vehicleexterior information detection unit 12030 causes the imaging unit 12031to capture an image of the exterior of the vehicle and receives thecaptured image. The vehicle exterior information detection unit 12030may perform object detection processing or distance detection processingfor persons, vehicles, obstacles, signs, or text on a road surface onthe basis of the received image.

The imaging unit 12031 is an optical sensor that receives light andoutputs an electrical signal corresponding to the amount of the receivedlight. The imaging unit 12031 can also output the electrical signal asan image and distance measurement information. In addition, lightreceived by the imaging unit 12031 may be visible light, or may beinvisible light such as infrared light.

The vehicle interior information detection unit 12040 detectsinformation on the interior of the vehicle. For example, a driver statedetection unit 12041 that detects a driver's state is connected to thevehicle interior information detection unit 12040. The driver statedetection unit 12041 includes, for example, a camera that captures animage of the driver, and the vehicle interior information detection unit12040 may calculate a degree of fatigue or concentration of the driveror may determine whether or not the driver is dozing on the basis ofdetection information input from the driver state detection unit 12041.

The microcomputer 12051 can calculate a control target value of thedriving force generation device, the steering mechanism, or the brakingdevice on the basis of the information inside and outside the vehicleacquired by the vehicle exterior information detection unit 12030 or thevehicle interior information detection unit 12040, and output a controlcommand to the drive system control unit 12010. For example, themicrocomputer 12051 can perform cooperative control aiming at realizingfunctions of advanced driver assistance system (ADAS) including vehiclecollision avoidance or impact mitigation, follow-up traveling based onan inter-vehicle distance, vehicle speed maintenance traveling, vehiclecollision warning, vehicle lane deviation warning, and the like.

Further, the microcomputer 12051 can perform cooperative control for thepurpose of automated driving or the like in which autonomous travel isperformed without depending on an operation of a driver by controllingthe driving force generator, the steering mechanism, the braking device,and the like on the basis of information regarding the vicinity of thevehicle acquired by the vehicle exterior information detection unit12030 or the vehicle interior information detection unit 12040.

Furthermore, the microcomputer 12051 can output a control command to thebody system control unit 12020 on the basis of the vehicle exteriorinformation acquired by the vehicle exterior information detection unit12030. For example, the microcomputer 12051 can perform cooperativecontrol for the purpose of preventing glare, such as switching from ahigh beam to a low beam, by controlling the head lamp according to theposition of a preceding vehicle or an oncoming vehicle detected by thevehicle exterior information detection unit 12030.

The audio/image output unit 12052 transmits an output signal of at leastone of audio and an image to an output device capable of visually oraudibly notifying an occupant of a vehicle or the outside of the vehicleof information. In the example illustrated in FIG. 31 , an audio speaker12061, a display unit 12062, and an instrument panel 12063 areillustrated as output devices. The display unit 12062 may include, forexample, at least one of an on-board display and a heads-up display.

FIG. 32 is a diagram illustrating an example of positions at which theimaging unit 12031 is installed.

In FIG. 32 , a vehicle 12100 includes imaging units 12101, 12102, 12103,12104, and 12105 as the imaging unit 12031.

The imaging units 12101, 12102, 12103, 12104, and 12105 may be providedat positions such as a front nose, side-view mirrors, a rear bumper, aback door, and an upper part of a windshield in a vehicle interior ofthe vehicle 12100, for example. The imaging unit 12101 provided at thefront nose and the imaging unit 12105 provided at an upper part of thewindshield inside the vehicle mainly obtain front view images of thevehicle 12100. The imaging units 12102 and 12103 provided in theside-view mirrors mainly obtain side view images of the vehicle 12100.The imaging unit 12104 provided in the rear bumper or the back doormainly obtains a rear view image of the vehicle 12100. The front viewimages acquired by the imaging units 12101 and 12105 are mainly used fordetection of preceding vehicles, pedestrians, obstacles, trafficsignals, traffic signs, lanes, and the like.

FIG. 32 shows an example of imaging ranges of the imaging units 12101 to12104. An imaging range 12111 indicates an imaging range of the imagingunit 12101 provided at the front nose, imaging ranges 12112 and 12113respectively indicate the imaging ranges of the imaging units 12102 and12103 provided at the side-view mirrors, and an imaging range 12114indicates the imaging range of the imaging unit 12104 provided at therear bumper or the back door. For example, a bird's-eye view image ofthe vehicle 12100 as viewed from above can be obtained bysuperimposition of image data captured by the imaging units 12101 to12104.

At least one of the imaging units 12101 to 12104 may have a function forobtaining distance information. For example, at least one of the imagingunits 12101 to 12104 may be a stereo camera constituted by a pluralityof imaging elements or may be an imaging element having pixels for phasedifference detection.

For example, the microcomputer 12051 can extract, particularly, aclosest three-dimensional object on a path through which the vehicle12100 is traveling, which is a three-dimensional object traveling at apredetermined speed (for example, 0 km/h or higher) in the substantiallysame direction as the vehicle 12100, as a preceding vehicle by acquiringa distance to each of three-dimensional objects in the imaging ranges12111 to 12114 and temporal change in the distance (a relative speedwith respect to the vehicle 12100) on the basis of distance informationobtained from the imaging units 12101 to 12104. Furthermore, themicrocomputer 12051 can set an inter-vehicle distance to be secured infront of the preceding vehicle in advance, and perform automatic brakecontrol (including following stop control), automatic accelerationcontrol (including following start control), and the like. Thus, it ispossible to perform cooperative control for the purpose of, for example,autonomous driving in which the vehicle autonomously travels withoutrequiring the driver to perform operations.

For example, the microcomputer 12051 can classify and extractthree-dimensional object data regarding three-dimensional objects intotwo-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians,and other three-dimensional objects such as utility poles on the basisof distance information obtained from the imaging units 12101 to 12104and use the three-dimensional object data for automatic avoidance ofobstacles. For example, the microcomputer 12051 classifies obstacles inthe vicinity of the vehicle 12100 into obstacles that can be visuallyrecognized by the driver of the vehicle 12100 and obstacles that aredifficult to visually recognize. Then, the microcomputer 12051 candetermine a risk of collision indicating the degree of risk of collisionwith each obstacle, and can perform driving assistance for collisionavoidance by outputting a warning to a driver through the audio speaker12061 or the display unit 12062 and performing forced deceleration oravoidance steering through the drive system control unit 12010 when therisk of collision has a value equal to or greater than a set value andthere is a possibility of collision.

At least one of the imaging units 12101 to 12104 may be an infraredcamera that detects infrared light. For example, the microcomputer 12051can recognize a pedestrian by determining whether or not a pedestrian ispresent in images captured by the imaging units 12101 to 12104. Suchrecognition of a pedestrian is performed by, for example, a procedure ofextracting a feature point in captured images of the imaging units 12101to 12104 serving as infrared cameras, and a procedure of performingpattern matching processing on a series of feature points indicating thecontour of an object to determine whether or not the object is apedestrian. When the microcomputer 12051 determines that a pedestrian ispresent in the captured images of the imaging units 12101 to 12104 andrecognizes the pedestrian, the audio/image output unit 12052 controlsthe display unit 12062 such that a square contour line for emphasis issuperimposed on the recognized pedestrian and is displayed. In addition,the audio/image output unit 12052 may control the display unit 12062 sothat an icon or the like indicating a pedestrian is displayed at adesired position.

The example of the vehicle control system to which the technologyaccording to the present disclosure is applied has been described above.The technology according to the present disclosure can be applied to thevehicle exterior information detection unit 12030 and the imaging unit12031 among the above-described components. Specifically, the lightreceiving element 1 or the distance measurement module 500 can beapplied to a distance detection processing block of the vehicle exteriorinformation detection unit 12030 and the imaging unit 12031. By applyingthe technology according to the present disclosure to the vehicleexterior information detection unit 12030 and the imaging unit 12031, itis possible to measure a distance to an object such as a person, avehicle, an obstacle, a sign, or a character on a road surface with highaccuracy, and it is possible to reduce a driver's fatigue and improvethe safety level of a driver and a vehicle by using obtained distanceinformation.

Embodiments of the present technology are not limited to theabove-described embodiments, and various modifications can be madewithout departing from the gist of the present technology.

Further, in the above-described light receiving element 1, an example inwhich electrons are used as signal carriers has been described, butholes generated by photoelectric conversion may be used as signalcarriers.

For example, in the pixel 10 of the above-described light receivingelement 1, a configuration in which all or some of the configurationexamples are arbitrarily combined can be adopted.

The effects described in the present specification are merely examplesand are not limited, and there may be effects other than those describedin the present specification.

The present technology can employ the following configurations.

(1)

A light receiving element including:

a semiconductor layer in which photodiodes performing photoelectricconversion of infrared rays are formed in units of pixels; and

a wiring layer in which a transfer transistor reading charge generatedby the photodiodes is formed,

wherein an inter-pixel light shielding unit that shields the infraredrays is formed at a pixel boundary portion of the wiring layer.

(2)

The light receiving element according to (1),

wherein the wiring layer includes one or more metal films, and theinter-pixel light shielding unit is formed on a side closer to thesemiconductor layer than the metal film closest to the semiconductorlayer.

(3)

The light receiving element according to (2),

wherein the inter-pixel light shielding unit is formed at a position ofthe same layer as that of a gate contact that connects a gate of thetransfer transistor and the metal film closest to the semiconductorlayer.

(4)

The light receiving element according to (3),

wherein the inter-pixel light shielding unit is formed at the same timewhen the gate contact is formed.

(5)

The light receiving element according to any one of (1) to (4),

wherein the wiring layer includes a reflection film disposed such thatat least a portion thereof overlaps the photodiode when seen in a planview, and the inter-pixel light shielding unit is formed of the samematerial as that of the reflection film.

(6)

The light receiving element according to any one of (1) to (4),

wherein the wiring layer includes a reflection film disposed such thatat least a portion thereof overlaps the photodiode when seen in a planview, and the inter-pixel light shielding unit is formed of a materialdifferent from that of the reflection film.

(7)

The light receiving element according to any one of (1) to (6),

wherein the inter-pixel light shielding unit is configured by disposinglight shielding members at predetermined intervals on a boundary line ofthe pixel when seen in a plan view.

(8)

The light receiving element according to any one of (1) to (6),

wherein the inter-pixel light shielding unit is configured by disposinglight shielding members, which have a linear shape long in a directionof a boundary line of the pixel, at predetermined intervals on theboundary line when seen in a plan view.

(9)

The light receiving element according to any one of (1) to (6),

wherein the inter-pixel light shielding unit is configured by disposinglight shielding members on a boundary line of the pixel so as tosurround an entire circumference of the pixel when seen in a plan view.

(10)

The light receiving element according to any one of (1) to (9),

wherein on-chip lenses are formed in units of pixels on a rear surfaceside opposite to a surface on which the wiring layer of thesemiconductor layer is formed.

(11)

The light receiving element according to (10),

wherein a moth eye structure is formed on the rear surface side of thesemiconductor layer.

(12)

The light receiving element according to any one of (1) to (11),

wherein two transfer transistors including a first transfer transistorand a second transfer transistor are formed in the semiconductor layer,

the first transfer transistor transfers charge generated by thephotodiodes to a first charge accumulation portion, and

the second transfer transistor transfers charge generated by thephotodiodes to a second charge accumulation portion.

(13)

The light receiving element according to any one of (1) to (12),

wherein the semiconductor layer further includes an inter-pixelseparation portion which is dug into at least a portion of thesemiconductor layer in a depth direction at the pixel boundary portion.

(14)

A distance measurement module including:

a predetermined light generation source; and

a light receiving element,

wherein the light receiving element includes

a semiconductor layer in which photodiodes performing photoelectricconversion of infrared rays are formed in units of pixels, and

a wiring layer in which a transfer transistor reading charge generatedby the photodiodes is formed, and

an inter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.

(15)

Electronic equipment including;

a distance measurement module including

a predetermined light generation source; and

a light receiving element,

wherein the light receiving element includes

a semiconductor layer in which photodiodes performing photoelectricconversion of infrared rays are formed in units of pixels, and

a wiring layer in which a transfer transistor reading charge generatedby the photodiodes is formed, and

an inter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.

REFERENCE SIGNS LIST

-   1 Light receiving element-   10 Pixel-   21 Pixel array portion-   M1 First metal film-   M2 Second metal film-   M3 Third metal film-   PD Photodiode-   41 Semiconductor substrate-   42 Multi-layered wiring layer-   44 Boundary portion (pixel boundary portion)-   45 Inter-pixel light shielding film-   47 On-chip lens-   61 Inter-pixel separation portion-   62 Insulating interlayer film-   63 Reflection film-   65 Inter-pixel light shielding unit-   66 Gate contact-   67 Metal wiring-   71 Inter-pixel separation portion-   111 Moth eye structure portion-   141 (141P, 141M) Reflection film-   161 Moth eye structure portion-   181 Dummy contact-   500 Distance measurement module-   511 Light emission unit-   513 Light receiving unit-   601 Smartphone

What is claimed is:
 1. A light receiving element, comprising: asemiconductor layer in which photodiodes performing photoelectricconversion of infrared rays are formed in units of pixels; and a wiringlayer in which a transfer transistor reading charge generated by thephotodiodes is formed, wherein an inter-pixel light shielding unit thatshields the infrared rays is formed at a pixel boundary portion of thewiring layer.
 2. The light receiving element according to claim 1,wherein the wiring layer includes one or more metal films, and theinter-pixel light shielding unit is formed on a side closer to thesemiconductor layer than the metal film closest to the semiconductorlayer.
 3. The light receiving element according to claim 2, wherein theinter-pixel light shielding unit is formed at a position of the samelayer as that of a gate contact that connects a gate of the transfertransistor and the metal film closest to the semiconductor layer.
 4. Thelight receiving element according to claim 3, wherein the inter-pixellight shielding unit is formed at the same time when the gate contact isformed.
 5. The light receiving element according to claim 1, wherein thewiring layer includes a reflection film disposed such that at least aportion thereof overlaps the photodiode when seen in a plan view, andthe inter-pixel light shielding unit is formed of the same material asthat of the reflection film.
 6. The light receiving element according toclaim 1, wherein the wiring layer includes a reflection film disposedsuch that at least a portion thereof overlaps the photodiode when seenin a plan view, and the inter-pixel light shielding unit is formed of amaterial different from that of the reflection film.
 7. The lightreceiving element according to claim 1, wherein the inter-pixel lightshielding unit is configured by disposing light shielding members atpredetermined intervals on a boundary line of the pixel when seen in aplan view.
 8. The light receiving element according to claim 1, whereinthe inter-pixel light shielding unit is configured by disposing lightshielding members, which have a linear shape longest in a direction of aboundary line of the pixel, at predetermined intervals on the boundaryline when seen in a plan view.
 9. The light receiving element accordingto claim 1, wherein the inter-pixel light shielding unit is configuredby disposing light shielding members on a boundary line of the pixel soas to surround an entire circumference of the pixel when seen in a planview.
 10. The light receiving element according to claim 1, whereinon-chip lenses are formed in units of pixels on a rear surface sideopposite to a surface on which the wiring layer of the semiconductorlayer is formed.
 11. The light receiving element according to claim 10,wherein a moth eye structure is formed on the rear surface side of thesemiconductor layer.
 12. The light receiving element according to claim1, wherein two transfer transistors including a first transfertransistor and a second transfer transistor are formed in thesemiconductor layer, the first transfer transistor transfers chargegenerated by the photodiodes to a first charge accumulation portion, andthe second transfer transistor transfers charge generated by thephotodiodes to a second charge accumulation portion.
 13. The lightreceiving element according to claim 1, wherein the semiconductor layerfurther includes an inter-pixel separation portion which is dug into atleast a portion of the semiconductor layer in a depth direction at thepixel boundary portion.
 14. A distance measurement module, comprising: apredetermined light generation source; and a light receiving element,wherein the light receiving element includes a semiconductor layer inwhich photodiodes performing photoelectric conversion of infrared raysare formed in units of pixels, and a wiring layer in which a transfertransistor reading charge generated by the photodiodes is formed, and aninter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.
 15. Electronicequipment, comprising: a distance measurement module including apredetermined light generation source; and a light receiving element,wherein the light receiving element includes a semiconductor layer inwhich photodiodes performing photoelectric conversion of infrared raysare formed in units of pixels, and a wiring layer in which a transfertransistor reading charge generated by the photodiodes is formed, and aninter-pixel light shielding unit that shields the infrared rays isformed at a pixel boundary portion of the wiring layer.